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Bureau of Mines Information Circular/1985 



Improved Stench Fire Warning 
for Underground Mines 

By William H. Pomroy and Terry L. Muldoon 




UNITED STATES DEPARTMENT OF THE INTERIOR 



c 
9^ 



75 



1^/NES 75TH A^^'^ 



Information Circular 9016 

Improved Stench Fire Warning 
for Underground Mines 

By William H. Pomroy and Terry L. Muldoon 




UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Model, Secretary 

BUREAU OF MINES 
Robert C. Morton, Director 







UNIT OF MEASURE ABBREVIATIONS 


USED IN 


THIS REPORT 






atm 


atmosphere, standard 


Vim 


micrometer 




°F 


degree Fahrenheit 


pet 


percent 






ft 


foot 


ppb 


part per billion 




ft5 


cubic foot 


ppm 


part per million 




ft^/min 


cubic foot per minute 


psi • 


pound per 


square 


inch 


h 


hour 


psla 


pound per 
absolute 


square 


inch, 


in 


inch 














psig 


pound per 


square 


inch. 


lb 


pound 




gauge 






Ib/MMft^ 


pound per million 
cubic foot 


s 


second 










wt pet 


weight percent 




mg/kg 


milligram per kilogram 


yr 


year 






mi 


mile 










min 


minute 











Library of Congress Cataloging in Publication Data: 



Pomroy, William H 














Improved stench fire warning for 


underg 


roun 


d mines. 








(Information circular / United 


States 


Dc 


partment of 


the 


Interior, 


Bureau of Mines ; 9016) 














Bibliography: p. 33. 














Supt. of Docs.: I 28.27:9016. 














1. Mine fires— Prevention and control. 


2, 


Stench firc- 


warning 


sys- 


tems in mines. I. Muldoon, T. L. 


II. T 


tie. 


III. Series 


In 


formation | 


circular (United States. Bureau of V 


ines ; 


9016) 








TN295.U4 [TN315] 622s 


[622' 


.8] 


84-600274 










CONTENTS 

Page 

Abstract 1 

Introduction 2 

"^ Alternatives to stench warning 4 

0^ Electrical systems 4 

^ Messenger systems 4 

^ Radio systems 4 

J* Deficiencies of existing stench warning systems 5 

Development of improved stench system 6 

.^^ Selection of stench agent 6 

^ Stench injector development 8 

Existing stench-inj ection methods 8 

Design concepts 8 

Pressurized canister with metering orifice 11 

Pressure balanced with metering orifice 12 

Variable-rate injection pump 14 

Concept evaluation 14 

Testing the improved stench system 16 

Laboratory testing >. 16 

Field testing 16 

Mine ventilation and compressed-air analysis 16 

Injector locations and installation 17 

Test procedures 18 

Results 19 

Design and development of second-generation stench injector 25 

Deficiencies in design of the improved stench injector 25 

Design features of the second-generation injector 26 

Remote-control system for injector actuation 27 

Testing of second-generation stench system 28 

Installation 28 

Test procedures 28 

Results 28 

Summary and conclusions 30 

References 33 

ILLUSTRATIONS 

1. Evacuation time versus maximum depth of main shaft 2 

2. Size of underground workforce versus depth of mine 3 

V) 3. Reactivity of ethyl mercaptan with iron oxide 5 

^ 4. Vial-breaking stench injector 10 

rv^ 5. Components of vial-breaking stench injector 10 

'^ 6. Pressurized-canister stench injector 11 

\ 7. Components of pressurized-canister stench injector 12 

V9 8. Pressurized-canister injector with metering orifice 12 

9. Use of pressure-balancing line to equalize pressure across metering 

Vo orifice 13 

10. Variable-rate injection pump 14 

11. Improved stench injector design 15 

12. Layout of haulage levels, boreholes, and main shaft in test mine 17 

13. Sampling points and transit times for compressed-air system tracer gas 
analysis 18 

14. Main shaft ventilation-air injector location 18 



^ 



XI 



ILLUSTRATIONS—Continued 

Page 

15. Remote venthole injector location 18 

16. Compressed-air injector location 19 

17. Compressed-air injector mounted on receiver tank 20 

Stench test results, improved system, first shift: 

18. 1-4 level 20 

19. 1-5 level 21 

Stench test results, improved system, second shift: 

20. 1-4 level 21 

21. 1-5 level 21 

Stench test results, existing system, third shift: 

22. 1-4 level 22 

23. 1-5 level 22 

Previous stench test results, existing system, first shift: 

24. 1-4 level 22 

25. 1-5 level 23 

Previous stench test results, existing system, second shift: 

26. 1-4 level 23 

27. 1-5 level 23 

28. Locations of air sampling points 24 

29. Stench concentration versus time for air samples collected during stench 

tests 25 

30. Refilling improved stench injector 26 

31. Second-generation stench injector design 26 

32. Refilling second-generation injector 27 

33. Second-generation injector for compressed air 29 

34. Second-generation injector for ventilation air installed at main shaft.. 29 

35. Wireless remotely controlled stench injector for ventilation air in- 

stalled at remote venthole 30 

36. Master panel installed in hoist room 30 

37. Remote-control telemetry system installed on leg of emergency-escape- 

hoist headf rame at remote venthole 31 

Stench test results, second-generation system, first shift: 

38. 1-4 level 32 

39. 1-5 level 32 

Stench test results, second-generation system, second shift: 

40. 1-4 level 32 

41. 1-5 level 33 

TABLES 

1. Properties of industrial gas odorants evaluated against ethyl mercaptan. 7 

2. Stench fire-warning system specifications 9 

3. Evaluation matrix for new injection-method design concepts 16 



IMPROVED STENCH FIRE WARNING FOR UNDERGROUND MINES 

By William H. Pomroy and Terry L. Muldoon 



ABSTRACT 

This report describes Bureau of Mines research that led to the de- 
sign, prototype fabrication, and successful proof-of-concept testing of 
an improved stench fire-warning system for underground noncoal mines. 

Stench systems are the most widely used means of warning miners in 
underground noncoal mines of fires or other emergencies. A stench sys- 
tem alerts miners that an emergency condition exists by injepting an 
odorant into the mine air. Although stench warning systems have been 
used successfully for over 60 yr , present systems suffer several seri- 
ous shortcomings, including odorant toxicity, unreliability of warn- 
ings, widely varying stench concentrations, and others. 

In 1980, the Bureau began a research program to upgrade the stench 
warning system. The resultant system overcomes the deficiencies of ex- 
isting systems by substituting tetrahydrothiophene for the commonly 
used ethyl mercaptan stench odorant, and through the use of a specially 
designed stench injector. The improved injector reliably meters stench 
fluid into either ventilation-air or compressed-air streams at a pre- 
cisely controlled rate. Prototype hardware has been fabricated and 
proof-of-concept tested under both laboratory and in-mine conditions. 



^Supervisory mining engineer, Twin Cities Research Center, Bureau of Mines, Minne- 
apolis, MN . 

^Program manager, Foster-Miller Associates, Inc., Waltham, MA. 



INTRODUCTION 



Fires In underground noncoal mines are 
a serious hazard to life and property. 
From 1965 to 1979, there were 115 report- 
able fires (at least 30 min in duration 
or resulting in injury) in U.S. under- 
ground noncoal mines, accounting for 119 
fatalities (J_).-^ Countless millions of 
dollars were spent on rescue and recovery 
efforts, equipment repair and replace- 
ment, and mine rehabilitation. In addi- 
tion, mines shut down by fires were 
forced to forego hundreds of millions of 
tons of mineral production. 

^Underlined numbers in parentheses re- 
fer to items in the list of references at 
the end of this report. 



The primary safety hazard in an under- 
ground fire is contaminated air. Since 
the mine's limited fresh-air supply can 
be rapidly consumed and replaced by smoke 
and toxic gas, the mine must be evacuated 
as quickly as possible in the event of 
fire. However, mine evacuation is often 
a very time-consuming process. 

In a recent survey of 50 underground 
noncoal mines, emergency evacuation times 
ranged from 5 to 85 min, with a strong 
correlation between the time required for 
evacuation and the maximum depth of the 
main shaft (fig. 1) (2^). Compounding the 
problem of longer evacuation times for 
deeper mines is the fact that work forces 
in deeper mines are usually larger than 



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20 



70 



30 40 50 60 

EVACUATION TIME, min 

FIGURE 1. - Evacuation time versus maximum depth of main shaft. 



work forces in shallower mines (fig. 2). 
The average work force in mines between 
3,600 and 7,700 ft deep is 195 miners per 
shift, whereas the average work force 
for mines less than 1,800 ft deep is only 
84 miners per shift. As mines become 
deeper with the depletion of shallower 
ore bodies , these problems of long evacu- 
ation times and more miner exposure to 
fire hazards will tend to get worse. 

Mine fire evacuation must begin as 
soon as possible after a fire has been 
detected. The miners must be warned, and 
they must then follow an emergency escape 
preplan. Since time is of the essence, 
detection, warning, and escape must all 
be accomplished as reliably and quickly 
as possible. However, fire-warning tech- 
nology, the essential link between detec- 
tion and evacuation, has not kept pace 
with advances in detection and evacuation 
planning. 

In a typical stench system, ethyl mer- 
captan, a highly odoriferous organic com- 
pound, is released from the surface into 



the compressed-air and/or ventilation- 
air streams of the mine. The liquid is 
quickly vaporized, and the stench is car- 
ried in the airstreams to the working 
areas underground. Miners, upon smelling 
the stench, evacuate the mine according 
to the emergency preplan. 

Although the stench system has been 
used successfully for over 60 yr, it suf- 
fers several serious shortcomings owing 
to certain chemical properties of ethyl 
mercaptan and certain performance char- 
acteristics and limitations of present 
injection systems. These shortcomings 
include (1) toxicity of the odorant which 
can lead to debility in miners; (2) re- 
activity of the odorant with iron ox- 
ide, which can result in unreliable warn- 
ings because the odor may fade when 
transported long distances in steel pipe; 
(3) lack of control over the rate of 
agent release into the airstream, with 
the result that some work areas may re- 
ceive unbearably high stench concen- 
trations while other areas are missed 



200 r- 



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1,800 3,600 

MINE SHAFT DEPTH, ft 

FIGURE 2. - Size of underground workforce versus depth of mine. 



7,200 



altogether; (4) lack of visual indica- 
tions of system status, valve positions, 
and proper system operation; and (5) ex- 
cessively long stench transit times. 

In 1980, the Bureau of Mines embarked 
on a research program to upgrade the 
stench warning system. The objectives of 
this program were to improve the safety. 



reliability, and effectiveness of stench 
systems. The work done under this pro- 
gram was accomplished through a research 
and development contract with Foster- 
Miller Associates, Inc., Waltham, MA O- 
4^) , and is described in detail in this 
report. 



ALTERNATIVES TO STENCH WARNING 



Although the primary thrust of the re- 
search program was to upgrade the stench 
system, the following sections are in- 
cluded to acquaint the reader with avail- 
able and near state-of-the-art mine warn- 
ing system options. Subsequent analyses 
of existing stench warning technology and 
the improved stench warning system devel- 
oped by the Bureau are more meaningful 
when considered in the context of mine 
warning systems in general. 

Two alternatives to stench systems are 
now used on a limited basis: electrical 
and messenger systems. Radio systems, 
although not in current use, are often 
mentioned as a possible successor to the 
stench system. 

ELECTRICAL SYSTEMS 

Electrical warning systems are used 
where compressed-air equipment is not 
used extensively and where ventilation 
velocities are low. Bells, flashing 
lights, gongs, and horns have been tried 
and have achieved limited success. How- 
ever, these systems are not effective 
when miners are working outside the vis- 
ible or audible range of the alarm or 
when mine power fails. Where electrical 
equipment is used extensively in the min- 
ing operation, interruption of the power 
supply has sometimes been used to signal 
an emergency. However, this system is 
also unreliable because power interrup- 
tions are common in many mines, and elec- 
trical equipment may not be in use when 
an emergency occurs. 

MESSENGER SYSTEMS 

A messenger system depends on the 
miners to physically communicate the 
emergency warning from person to person. 



Some mines use a messenger system as the 
primary warning system, but more commonly 
a messenger system is used as a backup to 
the primary system. Messenger systems 
are particularly common in small mines 
where personnel are not spread out over a 
large area and/or where telephone systems 
are both reliable and extensive. The 
chief disadvantage of the messenger sys- 
tem is the time required for the signal 
to be passed to each worker. 

RADIO SYSTEMS 

Prototypes of high frequency (HF) , 
very high frequency (VHF) , and ultrahigh 
frequency (UHF) leaky-feeder wireless 
radio-transmission communication systems 
have been constructed and tested in sev- 
eral noncoal underground mines. Although 
originally designed for the geometry of 
coal mines, it was hoped these systems 
would find application in noncoal mines 
as well. However, test results showed 
signal ranges were limited to 30 to 50 ft 
from the transmission cable (5) . 

An alternative to the leaky-feeder ap- 
proach is provided by medium frequency 
(MF) transmission. MF has the unique 
capability to couple into, and reradiate 
from, continuous conductors in the mine 
(rails, trolley lines, water pipes, air 
lines, phone lines, etc.) in such a way 
that these conductors become not only the 
transmission lines, but also the antenna 
system for the signals (6^). 

Although this parasitic coupling ef- 
fect provides greater signal-transmission 
coverage, in comparison with leaky-feeder 
systems, MF systems have problems in 
reliably receiving the transmitted sig- 
nal. Large, protruding antennas are re- 
quired on vehicular transceivers, and 
users of personal transceivers must wear 



a specially designed vest containing an 
antenna and radio-circuit modules. In 
addition, total mine coverage is not as- 
sured due to limits on signal range and 
through-the-rock transmission. Miners in 



remote stopes and development headings 
that are not linked to the rest of the 
mine by continuous conductors are most 
vulnerable, yet typically they are faced 
with the longest evacuation times. 



DEFICIENCIES OF EXISTING STENCH WARNING SYSTEMS 



The air-carried-stench system is the 
most popular means of emergency warning 
in noncoal mines because it is the most 
practical, versatile, and effective means 
currently available. Despite several se- 
rious shortcomings , its use and accept- 
ance is widespread because the alterna- 
tives offer lower levels of safety and 
reliability. Stench system deficiencies 
addressed through this research include 
the following: 

1. Ethyl mercaptan is highly reactive 
with iron oxide (fig. 3). There- 
fore, the odor tends to fade when 
it is transported in steel pipe. 
(For this reason, ethyl mercaptan 
is no longer used as an odorant in 
the natural gas industry.) 

2, Ethyl mercaptan is highly toxic. 
The 8-h time-weighted average con- 
centration limit (threshold limit 
value, or TLV) established by the 



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80 120 

Time, min 
FIGURE 3. - Reactivity of ethyl mercaptan 
with iron oxide. 



200 



National Institute for Occupational 
Safety and Health (NIOSH) and the 
American Conference of Governmental 
and Industrial Hygienists (ACGIH) 
is 0.5 ppm. As a comparison, the 
NIOSH TLV for hydrogen cyanide is 
also 0.5 ppm. An absolute limit of 
2 ppm has been set by ACGIH for ex- 
posures of 15 min or less. In low 
concentrations, ethyl mercaptan can 
cause headaches and nausea. At 
higher levels, it can irritate the 
skin and eyes, affect liver func- 
tion, affect amino acid levels in 
the blood, and retard redox 
processes. 

3. The odor intensity of ethyl mercap- 
tan tends to increase steadily with 
increasing stench concentration. 
When personnel are exposed to high 
concentrations of stench, the odor 
can be overwhelming. 

4. Ethyl mercaptan is highly corro- 
sive to injection equipment and air 
lines. Prolonged use of ethyl mer- 
captan can damage injectors to the 
extent that proper function may be 
impaired. 

5. The injection methods release the 
stench in a totally uncontrolled 
fashion. As a result, areas of the 
mine near the injection point may 
be overwhelmed by the stench odor, 
and miners in those areas are like- 
ly to be exposed to potential- 
ly toxic concentrations of ethyl 
mercaptan. 

6. The injection methods have been un- 
reliable. Injection equipment is 
often "homemade" and "free lanced." 
"Designs" are often strongly influ- 
enced by the availability of mis- 
cellaneous parts at the mine site. 



Typical problems include operat- 
ing procedures that are complex 
and therefore improperly followed, 
frozen valves , mismatches in size 
and shape between major system 
components and stench-fluid refill 
containers, and unsatisfactory 
and/or incompatable materials of 
construction. 

Available injection equipment does 
not permit visual system status 
checks. An empty or nonfunctional 
injector is not readily apparent, 
and if unnoticed until needed dur- 
ing an actual emergency, precious 
time could be lost while refilling 
it or performing repairs. 

Current systems do not have visual 
indications of valve positions. It 
is difficult for personnel to know 
if valves are completely open or 
completely closed, especially when 
valves are frozen or sluggish. 

Available systems have no immediate 
visual indications of proper system 
operation. The only positive con- 
firmation that the odorant has been 
released is to contact personnel 
underground, and this is often a 
time-consuming process. 



10. 



Current systems seldom achieve to- 
tal mine coverage. Remote work- 
places, workplaces not using air 
equipment , and dead-end headings 
are often missed. 



11. 



Stench transport times 
acceptably long. 



can be un- 



In addition, certain functional defi- 
ciencies in the stench system are in- 
herent due to its reliance on moving 
airstreams to carry the warning signal. 
The heat-induced buoyancy effects of a 
mine fire, for example, may cause throt- 
tling or reversals of ventilation flows. 
Stench injected into intake air may be 
exhausted if the intake air flow is 
reversed. Areas with poor or slow ven- 
tilation and/or areas distant from 
compressed-air equipment may not receive 
the stench warning signal. It was beyond 
the scope of this research to treat such 
inherent limitations. However, as mines 
become deeper, as workings become more 
complex, and as diesel and electric 
equipment displace compressed-air equip- 
ment, the need for novel warning systems 
that will address these problems will 
grow. 



DEVELOPMENT OF IMPROVED STENCH SYSTEM 



The development of an improved stench 
system capable of safely, effectively and 
reliably warning underground personnel 
of an emergency was accomplished in two 
steps: First, a stench agent was se- 
lected; and second, an improved injector 
was developed. 

SELECTION OF STENCH AGENT 

A survey of industrial gas odorizing 
agents was undertaken to identify a suit- 
able substitute for ethyl mercaptan. 
Many compounds were surveyed, and five 
were selected for detailed evaluation: 
isopropyl mercaptan, amyl acetate (ba- 
nana oil), dimethyl sulfide, tertiary 
butyl mercaptan, and tetrahydrothiophene 
(THT). Factors considered were boiling 



point, freezing point, vapor pressure, 
flashpoint, flammability limits, reac- 
tivity, solubility in water, toxicity, 
odor threshold, availability, cost, and 
past industrial uses. The results of 
the final evaluations are summarized in 
table 1, 

THT emerged as the most desirable agent 
for use in the stench system. THT is 
widely used in Europe as a natural gas 
odorant and has been used successfully on 
a limited basis in this country for the 
same application. THT is not reactive 
with iron oxide, so it is not subject to 
"odor fade." The odor intensity of THT 
tends to stabilize at a moderate, easily 
recognizable level, and it is much less 
corrosive than ethyl mercaptan. 



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In addition, available data suggest 
that THT may be far less toxic than ethyl 
mercaptan. Although ACGIH and NIOSH have 
not established a TLV for THT, the lethal 
concentration (LC50) for inhaled vapors 
of THT is 44,200 ppm (for rats), compared 
with an LC50 of 4,420 ppm for ethyl mer- 
captan. Based on this finding, and a 
NIOSH search of its TOXLINE computer- 
ized data bank of toxic substances, the 
Mine Safety and Health Administration 
(MSHA) has approved the use of THT in 
mine stench systems, provided the injec- 
tion equipment maintains agent concen- 
trations at nontoxic levels, (The sub- 
stitution of THT for ethyl mercaptan in 
existing stench systems thus does not 
satisfy the conditions established by 
MSHA for the use of THT in mine stench 
fire-war ling systems), 

Othe"^ pertinent chemical and physical 
properties made THT a favorable choice 
for use in the stench system. However, 
like ethyl mercaptan, THT is flammable 
(flashpoint 55° F) and needs to be mixed 
with an inerting agent to avoid possible 
explosion hazards. This potential hazard 
is greatest if stench is injected into 
compressed air. Numerous incidences of 
compressor fires and explosions have been 
recorded. Most were caused by ignition 
sources, such as glowing carbon deposits, 
igniting combustible lubricating oils in- 
side the compressor, lines, or receiver. 
The introduction of a flammable liquid 
(such as a flammable stench odorant) into 
the compressed air system would only com- 
pound the hazard. 

Laboratory flammability tests were con- 
ducted, and it was determined that a mix 
of 10 parts Freon 113'^ refrigerant and 1 
part THT is totally noncombustible. Ac- 
cordingly, the stench fluid selected and 
used throughout the program was a 10:1 
mix of Freon 113 and THT. 

STENCH INJECTOR DEVELOPMENT 

Prior to hardware development, numer- 
ous mining companies and mine safety 
specialists were contacted to help 



set performance specifications for the 
improved stench warning system. Both 
performance-range and general design 
specifications were thus developed. The 
specifications are summarized in table 2, 
The development program began with a com- 
prehensive analysis of existing stench- 
injection systems. 

Existing Stench-Injection Methods 

Two methods of stench injection are now 
in common use: the vial-breaking method 
and the pressurized-canister method. The 
vial-breaking method employs a glass vial 
that contains the stench fluid. The vial 
is placed inside an airtight steel cylin- 
der (fig. 4), which is connected in par- 
allel to 'the compressed-air line by two 
hoses fitted with globe valves. The sys- 
tem is activated as follows: First, the 
globe valves are opened to allow air to 
pass over the vial; then, a steel plunger 
is screwed into the cylinder to break 
the vial (fig. 5). The broken vial re- 
leases the stench fluid into the air- 
stream. The practices of throwing a bot- 
tle of stench fluid down the ventilation 
shaft or "puddling" the fluid at the col- 
lar of the downcast shaft are simply mod- 
ified forms of the vial-breaking method. 

Where the pressurized-canister method 
is used, the stench fluid is contained in 
a canister pressurized to 400 psi with a 
fluorinated hydrocarbon propellant (fig. 
6). The canister is connected to the 
compressed-air line or emptied into the 
ventilation airstream through a short 
length of tubing (feed line in figure 7). 
Both, systems use an ethyl mercaptan-Freon 
mix as the stench agent. 

Functional analysis and actual experi- 
ence indicated that neither the vial- 
breaking method nor the pressurized- 
canister method was satisfactory because 
they were fundamentally unable to meet 
the established performance-range or gen- 
eral design specifications. Alternative 
design concepts were therefore developed. 

Design Concepts 



'^Reference to specific products does 
not imply endorsement by the Bureau of 
Mines. 



Three design concepts were developed 
and evaluated relative to the performance 
specifications: pressurized canister 



TABLE 2. - Stench fire-warning system specifications 
Performance-range specifications 

Airflow, ft^: 

Ventilation air 50,000-2,000,000 

Compressed air 2,000-20,000 

Compressed-air pressure psig. . 80-150 

Stench gas concentration, ppm: 

In compressed-air line '0.5-2.0 

In ventilation air '0.1-2.0 

Minimum duration of stench injection, min: 

Into compressed air 30 

Into ventilation air 10 

Air temperature, °F: 

Ventilation -30-125 

Compressed -30-200 

Equipment operating specifications: 

Temperature °F. . -30-125 

Humidity pet. . 20-100 

Vibration (applied) ' None 

Environmental corrosion pH. . 4.0-9.0 

General design specification 

Reliability Extremely high. (Sys- 

stem should be simple 
with a minimum number 
of moving parts.) 
Life expectancy Indefinite with per- 
iodic maintenance. 

Ease of operation Simple — requiring 

minimal training. 

System status indication Visual , including 

"Ready to operate," 
"Operating correct- 
ly," and "Needs to be 
refilled." 
Injector costs, maximum: 

Hardware ^$h , 900 

Installation worker-h. . 8 

Maintenance worker-h/month. . 0. 5 

'As an added safequard, the maximum design concentration of THT is the same as that 
of ethyl mercaptan, even though available data suggest that THT is far less toxic. 

^Median from field survey; however, a much lower figure is probably more realistic. 
This figure does not include telemetry for remote injector activation, although tele- 
metry may represent the single largest expense for remotely operated systems. 



10 




FIGURE 4. - Vial-breaking stench injector. 



Flexible hose 



Valve 




Stench fluid 



Vial-breaking plunger 



Screen 



FIGURE 5. - Components of vial-breaking stench injector. 



11 




FIGURE 6. - Pressurized-canister stench injector. 



with metering orifice, pressure balanced 
with metering orifice, and variable-rate 
injection pump. Each of these concepts 
is described below. 

Pressurized Canister 
With Metering Orifice 

This concept, which provides for meter- 
ing of the stench flow, is a logical 
extension of the pressurized-canister in- 
jection method already in use. The me- 
tering capability could be added simply 
by installing a metering orifice in the 
stench-delivery tube of a pressurized- 
canister injector (fig. 8). 

Although the design is simple and in 
theory could satisfy the system perform- 
ance specifications, injector reliability 



would be low. Low reliability would re- 
sult because an extremely small orifice 
would be required to meter the contents 
of the pressurized canister (at 400 psi) 
into the airstream over the desired time 
period (10 min for ventilation air; 30 
min for compressed air) . Internal canis- 
ter pressurization to at least 400 psi is 
necessary to assure complete discharge of 
the canister contents. Orifices sized 
O.OOI to 0.013 in would be required to 
achieve the desired stench flow rates. 
Particles as small as 25 vim could plug an 
orifice of this size, and the probability 
of encountering particles 25 yra in diam- 
eter or larger is very high, even in a 
clean environment. Since nothing ap- 
proaching clean-room conditions exists at 
a typical mine, the chances of a plugged 



12 




Stench canister 



Valve 



Feed line 



Bali valve 



Compressed-air line 



FIGURE 7. - Components of pressurized- 
canister stench injector. 



Manual valve 




Pressurized canister 



Pressure indicator 



Filter 



Solenoid valve 



Metering orifice 



FIGURE 8. • Pressurized-canister injector v/ith 
metering orifice. 



orifice (and, therefore, an interrupted 
stench discharge) are also very high. In 
addition, a wide variation in stench flow 
rate would result owing to canister pro- 
pellant pressure decay. The flow rate 
could be expected to vary by as much as 
50 pet over the period of the discharge. 

Pressure Balanced With Metering Orifice 

The pressure-balanced concept was de- 
veloped to take advantage of the positive 
features of the previous concept while 
eliminating its undesirable features. 
Orifices much larger than those mentioned 
above can be used if the high pressure 
differentials across the orifice are 
eliminated. This can be accomplished by 
introducing line pressure on both sides 
of the orifice via a pressure-balancing 
line. The concept is illustrated in 
figure 10. The pressure difference be- 
tween point 1 in figure 9 (just below the 
orifice at the entry to the pressure- 
balancing line) and point 2 (at the 
bottom of the standpipe) is negligibly 
small. 

During steady-state flow, the fluid 
pressure at point 2 is also roughly equal 
to the air pressure at point 1 because 
the fluid pressure and air pressure at 
point 2 are in equilibrium. Since the 
fluid pressure at point 2 is roughly 
equal to the air pressure at point 1 , the 
driving head exerted at the orifice is 
equal only to the weight of the column of 
fluid between point 2 and the orifice. 
This driving head remains constant for 
nearly the entire discharge, meaning the 
flow through the orifice (the stench- 
injection rate) is also constant during 
nearly the entire discharge. 

During startup, before the standpipe is 
emptied of stench mixture, the flow rate 
is greater than the steady-state flow 
value. This does not last very long and 
is easily minimized by making the stand- 
pipe cross-sectional area as small as 
possible. When the stench-mixture sur- 
face drops below the tip of the standpipe 
near the end of the run, the flow rate 
begins to decrease, since effective head 
decreases. Eventually, both the flow 
rate and effective head drop to zero. 



13 



Canister body 



Standpipe 



Mixture surface 




Pressure- 
balancing 
loop 



Airflow 
(very slow) 



Orifice 



Stench mixture stream 
(enters either compressed- 
air line or ventilation system) 

FIGURE 9. - Use of pressure-balancing line to equalize pressure across metering orifice. 



This effect can be lessened by minimizing 
the internal area of the canister below 
the tip of the standpipe. 

The important features of this concept 
are as follows: 

1. The pressure below the orifice is 
balanced by an equal pressure above 
the orifice so that the pressure of 
the airstream into which the stench 
is injected has no affect on injec- 
tor operation. 



The driving head across the orifice 
is very low, so the size of the 
orifice can be relatively large 
(0.015 to 0.070 in) and still 
achieve the desired stench flow 
rates. 

The driving head is independent of 
the amount of stench fluid in the 
injector canister. Therefore, the 
injection rate does not decay as 
the fluid level in the canister 
drops. 



14 



Variable-Rate Injection Pump 



Concept Evaluation 



The variable-rate injection pump con- 
cept is the most precise method for 
stench injection. A precision diaphragm 
metering pump placed between the stench 
canister and the airstream can effective- 
ly control stench-fluid flow rates to ex- 
tremely close tolerances (fig. 10). The 
primary disadvantages of this system are 
its complexity and its reliance on elec- 
tric power. These factors could lead to 
very low system reliability. In addi- 
tion, the cost of such a system would be 
quite high compared to that of the other 
two concepts. 



The three design concepts were sub- 
jected to a systematic evaluation to 
weigh their respective advantages and 
disadvantages. The concept-evaluation 
matrix showing the parameters evaluated 
and the resultant ratings is shown in ta- 
ble 3. Based on this evaluation, the 
pressure-balanced with metering orifice 
concept was selected for further develop- 
ment. Detailed design and prototype fab- 
rication followed. A drawing of the re- 
sulting injector is shown in figure 11, 
and operating data are shown in table 3. 



Pressurized canister 



Solenoid valve 



Volume-metering 
pump 

Electric motor 



Back-pressure valve 




Pressure indicator 



Filter 



Metering nozzle 



Manual valve 



FIGURE 10. - Variable-rate injection pump. 



15 



Standpipe 



Stench fluid 



Driving head 



Ball valve 



Pressure-balance line 




To compressed air or ventilation air 



FIGURE 11. - Improved stench injector design. 



16 



TABLE 3. - Evaluation matrix for new injection-method design concepts 



Parameter 


Pressurized 
canister with 


Pressure 
balance with 


Variable-rate 
injection pump 




metering orifice 


metering orifice 


Rating 


Value ' 




Rating 


Value' 


Rating 


Value' 




Stench concentration 

range. 

Complexity 

Filtration level required 
Number of injector sizes 

required. 

Status indication 

Ease of manual operation. 
Initial cost, estimated.. 
Operating cost, estimated 
Number of significant 

leak points. 
Electric power required.. 
Remote-operation 

capability. 
Temperature sensitivity.. 

Reliability 

Maintainability 

Training requirements.... 

Life expectancy 

Safety 


Acceptable 

Low 

Very high. 
5 

Fair 

Good 

$800 

$100 

15 

(2) 

Yes 

High 

Very low.. 

High 

Low 

High 

Medium. . . . 
NAp 


3 

3 



1 

2 
3 
3 

2 

1 

3 
3 

1 

3 
3 
3 
2 


Acceptable 

Low 

Medium. . . . 
3 

Fair 

Good 

$1,800.... 

$50 

1 


3 

3 
2 
2 

2 
3 
2 
3 
3 

3 
3 

3 
3 
3 
2 
3 
3 


Acceptable 

Medium. . . . 

High 

2 


3 

2 
1 
3 


Poor 

Good 

$3,000.... 

$100 

15 

Yes 

Yes 

Medium. . . . 

Low 

Low 

High 

Low 

Low 

NAp 


1 
3 

1 
2 
1 


(2) 

Yes 

Low 

High 

High 

Medium. . . . 

High 

High 

NAp 


1 
3 

2 

1 
1 
1 
1 
1 


Total 


36 


46 


28 



NAp Not applicable. 'Maximum total = 51. ^For remote-operation capability only, 



TESTING THE IMPROVED STENCH SYSTEM 



A prototype of the entire improved 
stench system was fabricated and proof- 
of-concept tested in the laboratory and 
at an operating underground mine to val- 
idate its performance and highlight any 
design deficiencies. 

LABORATORY TESTING 



FIELD TESTING 

The improved stench system was field 
tested at Kerr-McGee Corp.'s Church Rock 
No. 1 uranium mine near Gallup, NM. 

Mine Ventilation and 
Compr e ssed-Air Analysi s 



The system was thoroughly tested fol- 
lowing fabrication. Tests involved 
discharges of nonodorized liquids as 
well as the THT-Freon 113 mixture se- 
lected for stench warning use. Tests in 
both ventilation-air and compressed-air 
streams were performed. Parameters mea- 
sured included fluid flow rates, dis- 
charge times, and stench concentrations 
in the airstreams. All tests indicated 
conformance with the system performance 
specifications (table 2). 



The improved stench system releases 
odorant into both the ventilation-air and 
compressed-air streams, relying on these 
airstreams to transport the waraing sig- 
nal to the various workplaces. There- 
fore, a thorough knowledge of these sys- 
tems and their interactions was essential 
in order to plan and lay out an effective 
stench warning system. 

The test mine has two main levels, des- 
ignated 1-4 and 1-5, the 1-5 level being 
about 300 ft below the 1-4. Raises are 



17 



driven from these levels to the ore, 
which is 50 to 100 ft above the level in 
each case. Figure 12 presents the layout 
of the haulage levels, along with the lo- 
cations and flow rates of the ventilation 
shaft and boreholes. 

The ventilation scheme has intake air 
downcasting through the main shaft and 
borehole 6 to the haulage levels. The 
air travels along the haulage drifts, up 
the raises, through the stopes, and fi- 
nally through a network, of exhaust drifts 
in the ore horizon and out the exhaust 
boreholes. Exhausting fans are located 
on the surface at the exhaust boreholes. 

For both ventilation purposes and ad- 
ministrative reasons, the 1-4 level of 
the test mine is divided into two seg- 
ments. The area to the east of the two 
air doors (fig. 12) has its own hoist- 
ing plant, compressed-air supply, and 
ventilation system. The two doors form 
an airlock, and are normally closed; how- 
ever, there is a minor leakage flow 
from the east side to the west. The two 
compressed-air systems are connected, and 
there is normally a small net flow, again 
from east to west. Thus, the stench 



Venthole 2 
95,000 ftVmin 
upcast 

Main shoft ^ 

22!,00Gft7min^ 

total downcast 




1-4 level 



tests were conducted in the west side of 
the mine without disturbing the east 
side. 

A tracer gas technique was used to 
determine the effectiveness of the 
compressed-air system in transporting the 
warning signal. The tracer gas was re- 
leased at the point where the new stench 
injector was to be installed, at 9:55 
a.m. , a time when compressed-air usage 
is usually at a maximum. Starting at 
10:00 a.m., air samples were taken at 
3-min intervals for 30 rain, at four loca- 
tions underground and on the surface at 
venthole 1. 

Tracer gas was detected at all sampling 
points. The locations of the sampling 
points as well as the transit time of the 
tracer gas to each point are indicated in 
figure 13. 

The rapid appearance of the tracer gas 
in the exhaust borehole (after 8 min) in- 
dicated that leakage from the compressed- 
air line into the ventilation air was 
originating not very far downstream from 
the injection point and that the stench 
first reached most areas of the mine 
through the ventilation air rather than 
in the compressed air. It is also proba- 
ble that a large percentage of the stench 
injected into the compressed-air line was 
exhausted through venthole 1 after having 
passed through only a small part of the 
total workings. However, some stench was 
retained in the compressed air, indicat- 
ing that this mode of stench transport 
can effectively supplement ventilation- 
air transport. 

Injector Locations and Installation 



Venthole I 
35,000 ftVmin 
upcast 




Main shaft 
75,000 ftVmin 
upcast 



'Venthole 3 
85,000 ftVm in 
upcast 

1-5 level 



Venthole 6 
45,000 ftVmin 
downcost 



FIGURE 12. - Layout of haulage levels, boreholes, 
ond main shaft in test mine. 



Ventilation-air injectors were in- 
stalled at each of the two intake-air 
shafts. One injector was installed in a 
crawl space located just below ground 
level near the top of the main shaft 
(fig. 14). Because there was a high rate 
of activity near the employee and sup- 
ply hoist, the crawl space location was 
chosen to minimize the possibility of ac- 
cidental system activation. Approximate- 
ly 10 ft of copper tubing was suspended 
from the injector down into the shaft to 
carry the stench agent. 



18 




rrr 



LEGEND 
Main shaft 
Exhaust borehole 
Sampling pointin stope 
Sampling point on haulage level 
Transit time, minutes 



1-5 level 

FIGURE 13. - Sampling points and transit times for compressed-air system tracer gas analysis. 



Shaft collar 



Wire mesh 



Copper tube 



Intake air 




Shaft lining 



FIGURE 14. - Main shaft ventilation-air injector 
location. 

The other ventilation-air injector was 
installed on a leg of an emergency- 
escape-hoist headframe positioned over 
venthole 6 about 1 mi from the main shaft 
(fig. 15). This injector was mounted 
approximately 7 ft above ground level to 
discourage tampering. 




Injector 



Ventilation shiaft intake 



FIGURE 15. - Remote venthole injector location. 



The compressed-air injector was mounted 
on the main receiver for the compressed- 
air system (figs. 16-17). A piece of 
copper tubing approximately 2 ft long 
joined the injector to the main com^ 
pressed-air line through a shutoff valve. 

Test Procedures 

The in-mine test consisted of using the 
improved stench system to issue the warn- 
ing signal during two regularly scheduled 
fire drills. The mine's routine practice 
was to conduct drills during all three 



19 



From air compressor 




Injector 



Pressure-balancing line 



Compresses-air line to mine 



FIGURE 16. - Compressed-air injector location. 



shifts over the course of 1 week. The 
improved system was used for the drill 
during the first shift (day shift) and 
for the second-shift (afternoon) drill. 
For comparison, the mine's existing vial- 
breaking system was used for the third- 
shift drill. This arrangement afforded 
the opportunity to evaluate and compare 
the performance of the two systems under 
constant mine conditions. 

The emergency plan at the mine is dif- 
ferent from that of most mines in that it 
does not call for immediate evacuation. 
Standard procedures require miners to 
proceed to a dead-end drift or stope with 
an air line and build a barricade. 

The standard procedure for fire drills 
(of which the miners are always informed 
beforehand) requires miners to note the 
time they smell stench and proceed to a 
dead-end drift or stope with an air line 
and barricade materials. (Barricades are 
not actually built.) 

Environmental samplers visit each work 
area and fill out a form showing the 
location of each worker, the time he or 
she smelled stench, the strength of the 
stench, the action taken by the miner, 
and the miner's comments. This procedure 
was followed during all tests. 



Results 

The main criteria for evaluating the 
performance of the improved stench system 
were (1) degree of coverage, (2) elapsed 
time between actuation of the injectors 
and the detection of odor at various lo- 
cations, and (3) stench concentrations 
measured at various locations. 

To give an overall view of the perform- 
ance of both the improved system and the 
existing system, stench transit times to 
various areas of the mine were plotted on 
maps of the haulage levels. These tran- 
sit times were based on the stench arriv- 
al times recorded by the mine's environ- 
mental samplers during the drills. 

Figures 18-21 show the results of the 
tests of the improved system (during the 
first- and second-shift drills and on 
both haulage levels.) Figures 22 and 23 
show the results of the test of the 
existing system during the same week. 
Since this test was run on the third 
shift, there were fewer active workplaces 
for which arrival times could be re- 
corded. Therefore, the results of two 
earlier tests of the existing system 
were reconstructed from mine records to 
provide a better comparison of the old 



20 





FIGURE 17. - Compressed-air injector mounted 
on receiver tank. 



and new systems. The earlier tests of 
the mine's existing system are illus- 
trated in figures 24-27. 

During the first-shift test of the im- 
proved system, air samples were taken at 
several locations in the mine while the 
stench was noticeable at those locations. 
These samples were then analyzed to ob- 
tain their quantitative stench concentra- 
tions (expressed as parts per million of 
THT in air). The locations of the sam- 
pling points are shown in figure 28. 
Stench concentration versus time is 
plotted in figure 29. Figure 29 also 
shows the upper and lower system design 
limits for stench concentration (from 
table 2). Only 2 of the 10 samples col- 
lected exceeded the 2.0-ppm upper design 
limit, and no samples fell below the 0.1- 
ppm lower design limit. 

Of 23 miners who were interviewed dur- 
ing the second-shift test of the improved 
system, only 2 rated the stench as reach- 
ing an annoying level , and none rated it 
as reaching a sickening level, indicating 
that odorant levels were probably very 
near the 2.0-ppm design goal. One envi- 
ronmental sampler commented that the 
miners thought the new stench (THT) was 
not as sickening as the old (ethyl 
mercaptan) . 

Mine management was pleased with the 
improved system not only because of im- 
provement in warning times , but also be- 
cause of the ease and simplicity of oper- 
ation of the new injectors. The valve 




4 

10 



LEGEND 
Main shaft 

Sampling pointin stope 
Sampling pointon haulage level 
Transit time, minutes 



FIGURE 18. - Stench test results, improved system, first shift, 1-4 level. 



21 





LEGEND 
Main shaft 
1^ Sampling pointinstope 
4 Sampling point on haulage level 
10 Transittime, minutes 

FIGURE 19. - Stench test results, improved system, first shift, 1-5 level. 



^ 



i 



14 taNo smel 




LEGEND 
Main shaft 
^ Sampling point in stope 
4 Sampling pointon haulage level 
1 Transit time, minutes 



FIGURE 20. - Stench test results, improved system, second shift, 1-4 level. 





LEGEND 

<S) Main shaft 

^ Sampling point in stope 

5 Transittime, minutes 



FIGURE 21. - Stench test results, improved system, second shift, 1-5 level. 



22 




LEGEND 
(S) Main shaft 
^ Sampling point in stope 
4 Sampling point on haulage level 
10 Transittime, minutes 



FIGURE 22. - Stench test results, existing system, third shift, 1-4 level. 





LEGEND 
Main shaft 
^ Sampling pointon haulage level 
15 Transittime, minutes 

FIGURE 23. - Stench test results, existing system, third shift, 1-5 level. 




LEGEND 
(^ Main shaft 
■^ Sampling point in stope 
^ Sampling point on haulage level 
10 Transittime, minutes 



FIGURE 24. - Previous stench test results, existing system, first shift, 1-4 level. 



23 





LEGEND 
Main shaft 
1^ Sampling point in stope 
^ Sampling point on haulage level 
1 5 Transit time, minutes 

Previous stench test results, existing system, first shift, 1-5 level. 



smel 




4 

* 



LEGEND 
Main shaft 

Sampling pointin stope 
Sampling pointon haulage level 



1 5 Transit time, minutes 
FIGURE 26. - Previous stench test results, existing system, second shift, 1-4 level. 




30 
FIGURE 27 




LEGEND 
Main shaft 
W^ Sampling pointin stope 
^ Sampling point on haulage level 
10 Transittime, minutes 

Previous stench test results, existing system, second shift, 1-5 level. 



24 




1 -4 level 




LEGEND 

® Ventilation-air injection 
point 

p Sampling point in stope 



i 



Sampling point on haulage 



FIGURE 28. 



level 
2 Sampling point number 

Locations of air sampling points. 



stem that breaks the vial in the existing 
system is very difficult to turn. In ad- 
dition, it is necessary to open two globe 
valves whose positions are not readily 
apparent. The improved system, which re- 
quires only the manipulation, in any or- 
der, of two easy-to-turn 90° valves, was 
regarded as far superior. 

The most dramatic improvement in tran- 
sit times occurred at the western end of 
the 1-5 level. No doubt this was due to 
the injection of stench into intake ven- 
tilation air at venthole 6. Substantial 
improvement also occurred at the west- 
ern end of the 1-4 level. This was prob- 
ably due to the injection of stench into 
the intake air at the main shaft. In the 
central area of the 1-4 level, transit 



times for the two systems were about the 
same. The reason for this may have been 
that when the existing system was used, 
stench reached this area by leakage from 
the compresssed-air system into the ven- 
tilation air. This hypothesis is sup- 
ported by the rapid appearance of tracer 
gas that was observed in venthole 1 
during the tracer gas test of the 
compressed-air system. Both systems had 
some trouble providing rapid coverage to 
the area near the eastern boundary of the 
1-4 level. This area is at the extremes 
of both the ventilation and compressed- 
air systems. Changes in the ventilation 
system to increase airflow to these areas 
would probably improve coverage of these 
areas. 



25 



3 - 



E 
o. 

Q. 



o 
^ 2 



o 
o 







I 

▲ 




I 


I 

KEY 

A Sampling point No. 1 
■ Sampling point No. 2 












A 


o Sampling point No. 3 

Upper design 


limit 




A 




A 

■ 












o 


o 




° Lower design 


limit 






1 




1 


1 





10 



30 



20 
Tl ME, min 

FIGURE 29. - Stench concentration versus time for air samples collected during stench tests. 



40 



DESIGN AND DEVELOPMENT OF SECOND-GENERATION STENCH INJECTOR 



Field testing of the prototype stench 
system was successful in that the in- 
jectors performed according to specif- 
ication, providing faster, more consist- 
ent, and more controlled concentrations 
of stench in the mine. However, the 
field testing also highlighted certain 
design aspects of the injector needing 
improvement. 

DEFICIENCIES IN DESIGN OF THE IMPROVED 
STENCH INJECTOR 

The following deficiencies in the de- 
sign of the improved stench injector were 
noted : 

1. Fluid levels in the canister body 
were not visible, and valve posi- 
tions alone are not a reliable in- 
dicator of system readiness. An 
injector design that permits visual 
system status checks is needed. 



2. Refilling the injectors was a nui- 
sance. The injectors had to be 
removed from the mounting brackets 
and refilled from a special con- 
tainer (fig. 30). 

3. The injector had to be removed from 
the mounting bracket and dismantled 
to inspect the orifice and screen. 

4. Because two valves have to be 
opened, operation of the injector 
by remote control is somewhat com- 
plicated. (Remote-control injector 
operation is an extremely attrac- 
tive feature under certain circum- 
stances. In the field tests of 
the improved system, significantly 
shorter stench transit times were 
achieved in the part of the mine 
near the remote downcast vent 
shaft, due to the injection of 
stench into the ventilation 



26 





FIGURE 30. - Refilling improved stench injector. 

airstream at this location. But 
this time advantage would be lost 
if someone had to travel to the 
remote shaft during a mine emer- 
gency to manually operate the in- 
jector. The need for remote opera- 
tion is particularly acute where 
distance and/or inclement weather 
make timely access to a remote site 
impossible. ) 

5. The overall cost of the injector 
($1,800) was judged to be too high. 

DESIGN FEATURES OF THE 
SECOND-GENERATION INJECTOR 

The deficiencies listed above formed 
the basis for additional performance 
and general design specifications. Based 



^^ ven 



Filling 



Stench 
fluid 




Delivery tube to 
compressed oir or 
ventilation streom 



FIGURE 31. 
design. 



Second-generation stench injector 



on these additional specifications, a 
second-generation stench injector design 
was developed (fig. 31). Although func- 
tionally identical to the original injec- 
tor, the second-generation unit also sat- 
isfies these additional requirements: 

1. The canister body for ventilation- 
air injectors is made of clear 
polycarbonate, permitting visual 
inspection of the injector fluid 
level. Also, during injector oper- 
ation, bubbles can be seen rising 
through the fluid — proof positive 
of unhindered fluid flow, 

2. A refilling standpipe permits re- 
filling without removing the injec- 
tor from the mounting bracket (fig. 
32). 



27 



3. The orifice plate and screen can 
be quickly inspected through a 
port on the side of the injector. 

4. The injector is operated by a sin- 
gle easy-to-turn 90° ball valve. 



thus facilitating remote-control 
actuation. 

5. Widespread use of commercial compo- 
nents reduces the overall cost of 
the injector. 



REMOTE-CONTROL SYSTEM FOR INJECTOR ACTUATION 



As previously noted, improvements in 
stench times were greatest near the re- 
mote vent shaft. To insure that this 
rapid warning could be duplicated in an 
actual emergency, some form of remote- 
control injector operation would be 
required . 

The following performance specifica- 
tions were developed to guide the design 
of a remote system: 

1. The system telemetry must be wire- 
less or hard-wired, as conditions 
dictate. 

2. The system must provide positive 
feedback to the operator to indi- 
cate successful actuation of the 
injector(s) . 

3. The system must be capable of man- 
ual operation should remote opera- 
tion fail. 

4. The system telemetry must be capa- 
ble of being tested for continuity 
without actuating an injector. 

5. The system must provide emergency 
backup power to insure proper sys- 
tem function if mine power is lost. 

6. The system must be designed in ac- 
cordance with appropriate MSHA and 
National Fire Protection Associa- 
tion (NFPA) standards covering 
warning systems. 

7. The system must be designed to op- 
erate reliably in harsh mine en- 
vironments and not be adversely 
affected by dust, high humidity, 
varying temperatures, and electri- 
cal transients. 



8. The system must be capable of re- 
motely actuating one injector with 
the capability to add additional 
remote units if desired. 

The remote system described below was 
designed to satisfy the specific require- 
ments of the Kerr-McGee Church Rock No. 1 
Mine, where the second-generation stench 
system was field tested. However, the 
concept for the remote system is flexible 
and can be adapted to suit differing lo- 
cal conditions. 




^^• 





FIGURE 32. - Refilling second-generation injector. 



28 



Since no power or phone lines con- 
nect the site of the remote vent shaft 
with the mine office, a wireless (radio- 
frequency) remote-control system was se- 
lected. Wireless signal transmission be- 
tween the two sites was provided by a 
digital-scan-type telemetry system uti- 
lizing frequency-shift-keyed (FSK) tone 
telemetry. VHF FM radio transceivers 
were used to transmit signals between the 
two sites. 

Signals were transmitted between the 
two sites continuously to verify the 
functional readiness of the telemetry 
system. Fault lights were provided on a 
master control panel (master panel) to 
indicate telemetry failure, power loss, 



etc. Battery backup power was provided 
at the master panel and at the remote 
site. 

Operation of the remote injector was 
accomplished by depressing a button on 
the master panel. A digital coded signal 
was transmitted to the remote site, where 
it was received, decoded, and verified. 
The valve on the injector was then ro- 
tated. The rotation of this valve initi- 
ated the stench release and also tripped 
a switch that prompted the transmission 
of a return digital coded signal to the 
master panel. When the return signal was 
decoded and verified, a light appeared on 
the master panel, indicating that the in- 
jector valve had been operated. 



TESTING OF SECOND-GENERATION STENCH SYSTEM 



Prototypes of all the second-generation 
stench system components, including the 
remote system, were built and proof-of- 
concept tested in the laboratory and in 
the Church Rock No. 1 Mine. The in-mine 
tests of the complete system are summar- 
ized below. 

INSTALLATION 

One complete second-generation stench 
system, consisting of one manual com- 
pressed-air injector (fig. 33), one man- 
ual ventilation-air injector for the main 
shaft (fig. 34), and one wireless remote- 
control injector for the remote vent 
shaft (fig. 35) was installed at the 
Church Rock Mine. Antennas for the re- 
mote system were installed on top of the 
emergency-escape-hoist headframe at the 
remote site and on the roof of the hoist 
building near the main shaft. The two 
antennas were in a direct line-of-sight . 
The master panel (fig. 36) was installed 
in the hoist building within sight of the 
hoist operator. The telemetry equipment 
at the remote site (fig. 37) was mounted 
on a leg of the emergency-escape-hoist 
headframe near the injector. 

TEST PROCEDURES 

Following hardware checkout, two func- 
tional (fire-drill) tests of the system 



were conducted, one during the first 
shift and one during the second. (The 
mine was not working a third shift at the 
time of these tests). For both tests, 
all three injectors were actuated si- 
multaneously. The main shaft and com- 
pressed-air injectors were operated manu- 
ally. The injector at the vent shaft was 
actuated remotely at the same time by de- 
pressing the button at the master panel. 

RESULTS 

All three injectors and the remote ac- 
tuation system performed according to the 
specifications. The injector at the main 
shaft had a release time of 11-1/2 min, 
the injector at venthole 6 took 12-1/2 
min, and the compressed-air injector took 
32 min. The light on the master panel 
indicated successful actuation of the 
remote injector about 10 s after the re- 
lease button was depressed. 

The main criteria for evaluation of the 
second-generation stench system were 
(1) degree of coverage and (2) elapsed 
time between actuation of the injectors 
and the detection of the odor at various 
locations. Since the test conditions 
were almost identical to those present 
during the first-generation injector 
tests, air samples were not collected and 
analyzed for stench concentration. 



mm 



29 




FIGURE 33. - Second-generation injector for 
compressed air. 



FIGURE 34. - Second-generation injector for 
ventilation air installed at main shaft. 



30 




FIGURE 35. - Wireless remotely controlled 
stench injector for ventilation air installed 
at remote venthole. 

For the first-shift test, the elapsed 
times from actuation to detection ranged 
from 2 to 23 rain on both the 1-4 and 
1-5 levels (figs. 39-40). The maximum 
time was recorded at a location 3,400 ft 
from the remote vent shaft injection 
point on the 1-4 level. All recorded 
times compared closely to those recorded 





FIGURE 36. - Master panel installed inhoistroom. 

during the tests of the first-generation 
injector. 

During the second-shift tests, elapsed 
times ranged from 1 to 30 min on both the 
1-4 and 1-5 levels (figs. 40-41). Again, 
the maximum time was recorded at a loca- 
tion on the 1-4 level, 3,400 ft from the 
remote vent shaft injection point. 

Mine management was pleased with the 
improved injector design and the new re- 
filling system. Other significant im- 
provements over the original design were 
one-valve actuation, the clear bowl on 
the ventilation-air injectors, and a new 
orifice plug for easier orifice removal. 
Based on the success of the laboratory 
and field testing of this system, a pro- 
duction version is now being commercially 
marketed. The injector is available for 
about $1,300, and a THT refill kit is 
available for about $100. 



SUMMARY AND CONCLUSIONS 



An improved stench warning system for 
underground noncoal mines has been de- 
veloped and succesfully in-mine tested. 



The system utilizes a superior stench 
agent (THT) and employs an injector 
that dispenses a controlled volume of 



31 




FIGURF 37. - Remote-control telemetry system installed on leg of emergency-escape- 
hoist headframe at remote venthole. 



32 



Ventholee 
(g) . 



Venthole 1 
(g) 




LEGEND 
Main shaft 
l| Sampling point in stope 
4 Sampling point on haulage level 
10 Transit time, minutes 
FIGURE 38. - Stench test results, second-generation system, first shift, 1-4 level. 





FIGURE 39. 



LEGEND 
<S) Main shaft 
^ Sampling point in stope 
4 Sampling point on haulage level 
Ventholee io Transit time, minutes 

Stench test results, second-generation system, first shift, 1-5 level. 



Ventholee 
(8> 




LEGEND 
Main shaft 
i( Sampling point in stope 
4 Sampling point on haulage level 
10 Transit time, minutes 
FIGURE 40. - Stench test results, second-generation system, second shift, 1-4 level. 



^ 



33 




5 



Ve 



nthole 1 \ 



LEGEND 
Main shaft 

Sampling point in stope 
Transit time, minutes 



Venthole6 
FIGURE 41. - Stench test results, second-generation system, second shift, 1-5 level. 



stench fluid into either compressed or 
ventilation air. The system is simple, 
easy to use, requires little maintenance, 
is easy to recharge, and is designed for 



high reliability. It can be remotely op- 
erated by either wireless ' or hard-wired 
means. The system is commercially avail- 
able for about $1,300 per injector. 



REFERENCES 



1. Baker, R. M. , J. Nagy, L. B. McDon- 
ald, and J. Wishmyer. An Annotated Bi- 
bliography of Metal and Nonmetal Mine 
Fire Reports. Final report (contract 
J0295035, Allen Corp. of America). Vol- 
ume 1: BuMines OFR 68(1)-81, 1980, 64 
pp., PB 81-223729; Volume 2: BuMines OFR 
68(2)-81, 1980, 284 pp., PB 81-223737; 
Appendix: BuMines OFR 63(3)-81, 1980, 
390 pp. , PB 81-223745. 

2. FMC Corp. Mine Shaft Fire and 
Smoke Protection System. (Final report). 
Volume I. — Design and Demonstration (con- 
tract H0242016). BuMines OFR 24-77, 
1975, 407 pp.; NTIS PB 263 577. 

3. Muldoon, T. L. , T. Lewtas, and 
T. E. Gore. Upgrade Stench Fire Warning 
System — System Development and Prototype 
Tests (contract H02292002, Foster-Miller 
Associates, Inc.). BuMines OFR 136-81, 
1981, 142 pp.; NTIS PB 82-122128. 

4. Muldoon, T. L. , and K. Heller. Up- 
grade Stench Fire Warning System, Volume 



2 — Second Generation System Development 
and Prototype Test. Final report on Bu- 
Mines contract H0292002 with Foster- 
Miller Associates, Inc., 1983, 96 pp.; 
available upon request from William H. 
Pomroy, BuMines, Minneapolis, MN. 

5. Bergeron, A. A., R. L. Collins, and 
J. L. Michels. A Communication and Moni- 
toring System for an Underground Coal 
Mine, Iron Ore Mine, and Deep Underground 
Silver Mine (contracts S0133035 and 
J037 707 6, Rockwell Int.). BuMines OFR 
156-82, 1981, 293 pp.; NTIS PB 83-115865. 

6. Dobroski, H. , and L. G. Stolarszyk. 
A Whole-Mine Medium Frequency Radio Com- 
munications System. Paper in Proceedings 
of the 52nd Annual Technical Session 
(Mines Accident Prevention Association of 
Ontario, Toronto, Canada, May 25-27, 
1983). MAPAO, North Bay, Ont . , Canada, 
1983, pp. 3-15. 



«U.S. CPO: 1963-505-019/20^30 



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